Zip Code 78666
San Marcos, Texas — Hays County
📍 ZIP code 78666 is in San Marcos, Hays County, Texas.
ZIP code 78666 is located in San Marcos, Hays County, Texas. It is a zip code in the Central (CST/CDT) Time Zone with an estimated population of 87,775. The area code for ZIP code 78666 is 512.
Quick Answer
Zip code 78666 is in San Marcos, Texas (Hays County). It has a population of 87,775, median household income of $55,478, and median home value of $271,900.
Population
87,775
Income
$55,478
Home Value
$271,900
Climate
96°F / 39°F
About Zip Code 78666
Zip code 78666 is located in San Marcos, Texas, within Hays County. Home to approximately 87,775 residents, this area sits at an elevation of 711 ft and falls within the Central (CST/CDT) timezone. The local area code is 512.
The median household income is $55,478 per year, which is below the national median of $70,784. Homes in this zip code have a median value of $271,900, and the cost of living index is 81 (19% below the national average of 100).
Summers average a high of 96°F while winters drop to 39°F. The area receives about 37 in of rain annually. The zip code covers 176.6 square miles of land area and 0.9 square miles of water.
Key Statistics
87,775
$55,478
$271,900
Central (CST/CDT)
512
711 ft
176.6 sq mi
27
36,354
Advertisement
Compare With Nearby Zip Codes
| Metric | 78666 | 78655 | 78656 | 78670 | 78640 | 78130 |
|---|---|---|---|---|---|---|
| City | San Marcos, TX | Martindale, TX | Maxwell, TX | Staples, TX | Kyle, TX | New Braunfels, TX |
| Population | 87,775 | 3,687 | 2,953 | 178 | 71,460 | 95,787 |
| Median Income | $55,478 | $48,409 | $78,058 | $76,591 | $88,533 | $84,426 |
| Home Value | $271,900 | $223,000 | $194,900 | $233,300 | $291,100 | $296,300 |
| Cost of Living | 81 | 70 | 90 | 100 | 100 | 103 |
| Median Age | 27 | 46.6 | 32.6 | 40.4 | 33.3 | 35.9 |
Cost of Living
100 = National Average. San Marcos's cost of living is 19% below the national average.
vs. State Avg
Below
Affordability
Affordable
Income-to-Home
4.9x
Demographics
Zip code 78666 has a population of 87,775 people with a median age of 27. There are 36,354 housing units in this area.
Racial & Ethnic Composition
Source: U.S. Census Bureau American Community Survey estimates.
Population History
San Marcos (78666) population trend from 2010 to 2024
↑ 6.8%Source: U.S. Census Bureau estimates and American Community Survey data.
Climate & Weather
96°F
39°F
37 in
0 in
San Marcos experiences hot summers with average highs around 96°F. Winters are mild with lows averaging 39°F. The area receives virtually no snowfall.
Advertisement
Housing & Economy
Median Home Value
$271,900
Median Household Income
$55,478
With 36,354 housing units across 176.6 square miles, 78666 has a housing density of 206 units per square mile. The home price-to-income ratio is 4.9x.
Location & Geography
Latitude
29.8802°
Longitude
-97.9662°
Land Area
176.6 sq mi
Water Area
0.9 sq mi
Nearby Zip Codes
Zip codes closest to 78666 (San Marcos, TX) with distances:
Related Cities in Texas
Explore zip codes in other Texas cities:
ZIP Codes with Similar Income Nationwide
The five U.S. ZIP codes whose median household income is closest to 78666's $55,478. A way to compare San Marcos to economically similar communities elsewhere in the country.
Computed from U.S. Census Bureau ACS 5-Year Estimates by the Zip Code Near Me Data Team.
ZIP Codes with Similar Demographics
The five U.S. ZIP codes whose racial and ethnic composition most closely matches 78666 (San Marcos, TX). Similarity is measured by cosine distance on the five-category ACS demographic vector.
Computed from U.S. Census Bureau ACS 5-Year Estimates by the Zip Code Near Me Data Team.
Explore Texas
Popular "Near Me" Searches
Advertisement
People Also Ask
What zip code is San Marcos, Texas?
San Marcos, Texas uses zip code 78666.
What county is zip code 78666 in?
Zip code 78666 is located in Hays County, Texas.
What is the population of zip code 78666?
The population of zip code 78666 is 87,775 with a median age of 27.
Is 78666 in San Marcos, Texas?
Yes, zip code 78666 is in San Marcos, Hays County, Texas. The area code is 512.
Frequently Asked Questions
What city is zip code 78666 in?
Zip code 78666 is in San Marcos, Texas. It is part of Hays County and uses the Central (CST/CDT) timezone.
What is zip code 78666?
Zip code 78666 is a U.S. postal code in San Marcos, Texas (Hays County). It has a population of 87,775 and covers 176.6 square miles.
What is the population of zip code 78666?
The population of zip code 78666 (San Marcos, TX) is 87,775 with a median age of 27. There are approximately 36,354 housing units in this area.
What is the median income in zip code 78666?
The median household income in zip code 78666 (San Marcos, TX) is $55,478 per year. The cost of living index is 81 (100 = national average).
What is the average home price in zip code 78666?
The median home value in zip code 78666 (San Marcos, TX) is $271,900. The cost of living index is 81 compared to the national average of 100.
What county is zip code 78666 in?
Zip code 78666 is located in Hays County, Texas. The primary city is San Marcos.
What is the area code for zip code 78666?
Zip code 78666 in San Marcos, TX uses area code 512. It is located in the Central (CST/CDT) timezone.
Is zip code 78666 a good place to live?
Zip code 78666 (San Marcos, TX) has a cost of living index of 81 (100 = national average), a median household income of $55,478, and median home values of $271,900. The median age is 27. Visit the full page for demographics, climate, and nearby zip code comparisons.
What is the cost of living in zip code 78666?
The cost of living index for zip code 78666 (San Marcos, TX) is 81, where 100 represents the national average. This area is below the national average. Median home value: $271,900.
What schools serve zip code 78666?
Zip code 78666 in San Marcos, Texas is served by the local school district of Hays County. For specific school information, check your state's department of education or GreatSchools.org.
All demographic data on this page is sourced from the U.S. Census Bureau American Community Survey (ACS) 5-Year Estimates. ZIP code boundary and delivery data is sourced from the United States Postal Service (USPS). Data is updated periodically and may not reflect the most current figures. Census Bureau ZIP Code Tabulation Areas (ZCTAs) may differ slightly from USPS ZIP code boundaries.
People Also Searched For
Data Sources
- Population, income, housing, age, and demographics
- U.S. Census Bureau, American Community Survey 5-Year Estimates, 2019-2023 vintage.
- ZIP to city and county mapping
- USPS and HUD-USPS ZIP-County Crosswalk.
- Time zones and area codes
- IANA tz database and NANPA.
- Elevation
- U.S. Geological Survey National Elevation Dataset (NED), via the USGS Elevation Point Query Service. Mapped to each ZCTA centroid coordinates. Last refreshed 2026-05-19.
- Last refreshed
- 2026-05-18.